Prevalence and characterization of Vibrio cholerae isolated from shrimp products imported into Denmark

Abstract

A total of 3,555 metric tonnes of warm water shrimp were imported into Denmark from December 1994 to July 1995. V. cholerae O1 was not detected in any of the 748 samples analyzed. Non-O1 V. cholerae was found in a single (0.1%) cooked frozen shrimp product and in five (0.7%) raw frozen products, all originating from shrimp produced in aquaculture. Six isolated strains agglutinated in polyvalent O antisera, but did not agglutinate in Ogawa or Inaba antisera. The six strains were resistant to colistin and sulfisoxazole; three strains also showed resistance to ampicillin. None of the strains contained plasmids or genes encoding cholera toxin (CT) or heat- stable enterotoxin (NAG-ST). The absence of V. cholerae O1 and the low number of samples containing CT and NAG-ST negative non O1 strains in imported shrimp suggest that V. cholerae in such products may not constitute a public health problem.